I think this line is justified too.
The Seattle front four was with out Clemens but even with him it isn't as good as the 49ers. A big part of Atlanta's first half success was running the ball effectively, which I doubt will be the same against SF. There is lots of other position match ups but I think that's the big one.
However, the major factor that arouse from the last Falcons game was a lack of killer instinct. Instead of putting a team away it seems like they just coast. This should better argument when they are favorites but it doesn't change the fact that they aren't a rip your heart out team. So, I guess the character issue that popped up is bigger reason for their +4 then the actual game score.